The gentlemen and ladies at Sega who have toiled away lo these last several years on the Yakuza series aren't just one-trick ponies. For instance, series creator Toshihiro Nagoshi, long before he got into the whole Yakuza thing, also created the Super Monkey Ball series, and has worked on everything from Sonic to Billy Hatcher over the course of his career.
That said, apparently Nagoshi, alongside a number of his primary cohorts from the various Yakuza projects, are really into this whole Yakuza thing now. So much so, in fact, that they have formed their own studio. Appropriately titled "Yakuza Studio" (or Ryu ga Gotoku Studio), Nagoshi and posse will, predictably, be focusing on new entries in the Yakuza franchise, including a fifth Yakuza console title, and a new PSP game called Yakuza Black Panther 2.
According to a write-up from Andriasang (which they translated from the latest issue of Famitsu), Yakuza 5 is still extremely early in development, and details likely won't be slid in the direction of the press any time in the foreseeable future. Black Panther 2, however, is a bit further along, and focuses on the same protagonist as Yakuza Black Panther. Granted, that first PSP title never released outside of Japan, so the odds of this sequel coming to any other territories seem equally, if not more slim.
Despite the new moniker, Nagoshi and crew do plan to make games not named Yakuza once in a while. The team is still working on Binary Domain, a sci-fi action title set to release early next year. That game obviously has nothing to do with anything related to the Yakuza, but don't be surprised if Nagoshi decides to give the lead character a bitchin' full-back dragon tattoo or something, just to keep the theme going.